Problem: What do the following two equations represent? $4x-y = -4$ $4x+16y = 1$
Putting the first equation in $y = mx + b$ form gives: $4x-y = -4$ $-y = -4x-4$ $y = 4x + 4$ Putting the second equation in $y = mx + b$ form gives: $4x+16y = 1$ $16y = -4x+1$ $y = -\dfrac{1}{4}x + \dfrac{1}{16}$ The slopes are negative inverses of each other, so the lines are perpendicular.